1. Field
Apparatuses and methods consistent with exemplary embodiments relate to outputting audio, and more particularly, to an audio output apparatus capable of controlling a temperature of a voice coil, and a method thereof.
2. Description of the Related Art
Power may be supplied to an audio output apparatus such as a speaker at a level corresponding to that of an output level of the speaker. An increase in power corresponds to an increase in the output level of an audio signal. Electric current is introduced to a voice coil wound around a vibrating plate that transmits vibration to the atmosphere, and a temperature of the voice coil increases with the introduction of electric current. Accordingly, when an audio signal is output at high output level for a long period of time, the temperature of the voice coil increases to a melting point of a coating layer on the voice coil, causing problems such as damage to the voice coil.
To address the problem mentioned above, related audio output apparatus divides a digitized audio signal according to respective frequency bands, and estimate sizes of the output signals of the audio signals of the respective frequency bands that will be output through an amplifier. The audio output apparatus then estimates a temperature of the voice coil by applying the sizes of the output signals of the audio signals, to a pre-defined heating model algorithm. The audio output apparatus then controls the temperature rise of the voice coil by either decreasing or increasing the gains to adjust the output levels of the audio signal, depending on whether the estimated temperature of the voice coil exceeds a preset threshold or not.
However, because the voice coils generally have low heat capacity, the temperature of the voice coils rapidly decreases from high temperatures to an ambient temperature when an audio signal is not input. The heat capacity of the permanent magnet provided to generate vibration in response to electric current flowing on voice coil is about 200 times greater than that of the voice coil. Accordingly, the permanent magnet requires a longer time than the voice coil to increase or decrease in temperature.
However, there exists a generated error between the estimated temperature of the voice coil according to the method explained above and the actual temperature of the voice coil in a case when power is supplied to the audio output apparatus to drive it again in a state where the voice coil has a higher temperature than a room temperature. This error delays a control timing of gains and an adjustment of an audio signal output level, thus creating a risk of overheating of the voice coil.